Issue #2843778 by Wim Leers: EntityResource: Provide comprehensive test coverage for ContactForm entity

Issue #2843766 by arshadcn: EntityResource: Provide comprehensive test coverage for FieldConfig entity

Issue #2843775 by arshadcn, Wim Leers: EntityResource: Provide comprehensive test coverage for CommentType entity

Issue #2805281 by Wim Leers, damiankloip: ?_format=hal_json error responses are application/json, yet should be application/hal+json

Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method

Revert "Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method"

This reverts commit 59781ffc.

Issue #2737719 by Wim Leers, dawehner: EntityResource: Provide comprehensive test coverage: for every entity type, every format, every method